Normal baseband signals have an amplitude A(t) and a phase variation ΦP(t). For transmission there may be a need for an radio frequency (RF) carrier which contains a desired baseband information, i.e., s(t)=Re(A(t)ejΦp(t)ejωt). Thus, an upconverter is needed. For transmission, high power levels are needed, and to improve efficiency of the power amplifier (PA) switching PA concepts may be applied (e.g., class D). An important key problem for power amplifiers (PAs) is their efficiency. For this reason new concepts based on polar modulation, synchronous and asynchronous sigma-delta and combined pulse width and pulse phase modulation (PWM-PPM modulation) are of interest. Two-level or binary signals are very suitable in combination with switching PA's. For PWM-PPM modulation and high frequencies new modulators types have been proposed. In such modulators, the predistorted modulating signal can be directly modulated on the first harmonic of the PWM-PPM modulated signal. However, the PWM-PPM-based modulation methods mentioned above are in general sensitive to slewing distortions and especially in case of small duty cycles of the binary baseband signal. The pulse-shaping will change from a trapezium waveform (large duty cycle) of constant amplitude into a triangle waveform of varying amplitude for small duty cycles. This results in amplitude and phase distortions of the modulating signal at the radio frequency (RF) carrier of the PWM-PPM signal. In former ideas PWM & PPM modulator concepts have been proposed, which were suitable for these switching PA-concepts. In practice however and specially for RF high power levels, slewing will result in a performance degradation (distortion) of these PWM modulated signals.